The present technology relates to an optical-information recording medium and a playback apparatus for playing back it. More particularly, the present technology relates to an optical-information recording medium having a groove and a land that are alternately provided.
Optical discs to which information is recorded or from which information is played back using laser light have been put to practical use. Types of optical disc include a playback-only optical disc, a write-once optical disc, and a rewritable optical disc. With write-once and rewritable optical discs, address information indicating positions thereon is pre-recorded in order to enable recording of information.
Two types of system are available as a system for recording the address information. One of the systems is a system for recording the address information as preformat pits. The other system is a system for modulating (wobbling) signals provided by a groove. A track formed by the groove is called a “groove track”. The groove is a defined as a portion irradiated with laser light during manufacture of the optical disc. An area located between adjacent grooves is called a “land” and a track formed on the track is called a “land track”.
In recent years, it is desired that the recording capacity of optical discs be further increased. In order to increase the recording capacity, it is desired to employ a system for recording data to both of the groove track and the land track (this system is hereinafter referred to as a “land/groove recording system”, as appropriate). In the land/groove recording system, the address information on the groove track can be recorded by deflecting laser light during cutting.
In the land/groove recording system, an optical disc has been proposed which makes it possible to play back the addresses on both of the groove track and the land track. Japanese Unexamined Patent Application Publication No. 9-219024 discloses the following technology. When addresses are recorded to the groove track with a wobble, the addresses are intermittently recorded and the phases of the recording positions of the addresses are reversed between the adjacent group tracks. With such an arrangement, during playback of the wobble track, the previously recorded address information is intermittently played back, and during playback of the land track, the addresses on groove tracks at two opposite sides of and adjacent to the land track are alternately played back. Thus, wobble information (address information) can be obtained both during groove scan and during land scan.
Japanese Unexamined Patent Application Publication No. 2003-178464 and Japanese Unexamined Patent Application Publication No. 2006-228293 discloses the technologies. Each of the land track and the groove track is wobbled and wobbles are used to record address information to sidewalls of each track. In addition, address information blocks on a wobble track and address information blocks on a groove track are arranged offset in a track direction.